1. Field of the Invention
The present invention relates to circuit breakers and, more particularly, to a circuit breaker for a telecommunication system that includes a movable an having an offset.
2. Background Information
Circuit breakers for telecommunication systems typically are smaller than circuit breakers associated with power distribution networks. A typical telecommunication system circuit breaker measures 2.5 inches high by 2.0 inches long by 0.75 inch thick, when the circuit breaker is viewed with the operating handle extending horizontally and moving in a vertical arc. While having a reduced size, the telecommunication system circuit breaker must still accommodate the various components and devices (e.g., separable contacts; trip device; operating mechanism) associated with larger circuit breakers. Thus, while the conventional components of a telecommunication system circuit breaker may not be unique, the necessity of having a reduced size requires specialized configurations and robust components that are different than power distribution circuit breakers. This is especially true where the telecommunication system circuit breakers are used in environments wherein the circuit breaker may be expected to operate for over 10,000 operating cycles and 50 tripping cycles; however, the reduced size telecommunication system circuit breakers are typically limited to a current rating of 30 amps.
The telecommunication system circuit breaker is structured to be disposed in a multi-level rack. The rack has multiple telecommunication system circuit breakers on each level. The rack, preferably, has a spacing between the levels of 1.75 inches; however, the current structure of telecommunication system circuit breakers, as noted above, have a height of 2.5 inches. As such, users have been required to adapt the multi-level rack to accommodate the taller telecommunication system circuit breakers.
Circuit breakers disposed on the rack may be coupled to associated circuits. As such, if the current is interrupted in a first circuit, either due to the circuit breaker tripping or due to a user manually interrupting the circuit, it is sometimes desirable to interrupt the current on an associated second circuit. In the prior art, a common trip bar was structured to trip two adjacent circuit breakers. That is, a single trip bar extended across two circuit breakers and, if an over current condition occurred in either circuit, the actuation of the trip device caused the trip bar to rotate thereby tripping both circuit breakers. In smaller circuit breakers which have a low trip force, the use of a common trip bar is not feasible.
Thus, while existing telecommunication system circuit breakers are small, there is still a need for telecommunication system circuit breakers having a reduced height, especially a telecommunication system circuit breaker having a height of about, or less than, 1.75 inches; the preferred spacing between levels on the rack. However, as the size of the telecommunication system circuit breakers are reduced further, the need for robust, yet small, components which operate in a reduced space is increased. This is especially true for any component that extended, or moved, in the vertical direction. For example, in the prior art, the movable contact is disposed on a moving arm. The moving arm needed to move a sufficient distance to ensure that, when the separable contacts were separated, current could not arc between the fixed and movable contacts. The movable arm also traveled within an arc extinguisher. Typically, the moving arm was an elongated member which pivoted over a vertical arc. When the housing assembly had a height of 2.5 inches, the movable arm could be generally straight. Such a straight arm, however, would be incompatible with a shorter housing assembly. That is, due to the limited amount of space, and especially the limited height, in a shorter housing assembly, a straight moving arm would need to have a limited length and/or the housing assembly could not accommodate an arc extinguisher. Such a limited length movable arm would be too short to provide a sufficient gap between the separable contacts when in the open position. Alternatively, a generally straight movable arm structured to move over a reduced arc would not permit an arc generated during short circuit to dissipate. This failure to dissipate the arc would cause excessive damage to the separable contacts and or moving arm keeping the breaker from operating normally. Alternately having a significantly smaller contact gap would reduce the usable interruption rating of the breaker as not to be useful by industry. Accordingly, there is a need for a telecommunication system circuit breaker having a reduced size and an increased operating current range. There is a further need for a movable arm structured to operate in a telecommunication system circuit breaker having a reduced size while still providing a sufficient gap between the separable contacts when the contacts are in the open position.